Phone books can be great resources for confirming locations of your recent ancestors, but those big yellow doorstoppers are dying a slow death, the online newsmagazine Slate reports.

They've come a long way since the first phone directory, a one-pager listing all 52 telephone subscribers in New Haven, Conn., debuted in 1878. (The Slate article describes many more mentionable moments in phone-book history.)

The hefty, floppy books were created as vehicles for companies to sell advertising, and last year, 615 million directories were printed in the US, creating revenues of $13.9 billion, according to the Yellow Pages Association. But more and more cell phones are unlisted, and many people turn to the Internet to find phone numbers—especially people under 30. (For example, the last time I used a phone book was when the electricity in my apartment went out and I couldn't find the number I needed by text messaging Google.)

For more phone fun, OldTelephoneBooks.com has many old pictures of telephone books, and some are listed for sale. You can browse by country, state and city.